Computation is accepted as the third pillar supporting innovation and discovery in science and engineering and is central to NSF's future vision of Cyberinfrastructure Framework for 21st Century Science and Engineering (CF21)[1]. Software is an integral part of the computation paradigm and a primary modality for realizing the CF21 vision. Scientific discovery and innovation are advancing fundamentally new pathways opened by development of increasingly sophisticated software. Software is also directly responsible for increased scientific productivity and significant enhancement of researchers' capabilities. In order to nurture, accelerate and sustain this critical mode of scientific progress, NSF is establishing a new program, Software Infrastructure for Sustained Innovation (SI2), with the overarching goal of transforming innovations in research and education into sustained software resources that are an integral part of the cyberinfrastructure.

SI2 is a long-term investment focused on catalyzing new thinking, paradigms, and practices in using software to understand natural, human, and engineered systems. SI2's intent is to foster a pervasive cyberinfrastructure to help researchers address problems of unprecedented scale, complexity, resolution, and accuracy by integrating computation, data, networking and experiments in novel ways. It is NSF's expectation that SI2 investment will result in robust, reliable, usable and sustainable software infrastructure that is critical to the CF21 vision and will transform science and engineering.

It is expected that SI2 will generate and nurture the multidisciplinary processes required to support the entire software lifecycle and will result in the development of sustainable software communities. SI2 envisions vibrant partnerships among academia, government laboratories and industry for the development and stewardship of a sustainable software infrastructure that can enhance productivity and accelerate innovation in science and engineering. The goal of the SI2 program is to create a software ecosystem that includes all levels of the software stack and scales from individual or small groups of software innovators to large hubs of software excellence. The program addresses all aspects of CI, from embedded sensor systems and instruments, to desktops and high-end data and computing systems, to major instruments and facilities.

The SI2 program envisions three classes of awards:

1. Scientific Software Elements (SSE): SSE awards target small groups that will create and deploy robust software elements for which there is a demonstrated need, encapsulating innovation in science and engineering. The effort targeted by a SSE award is up to a level roughly comparable to: summer support for two investigators with complementary expertise; two graduate students; and their collective research needs (e.g. materials, supplies, travel) for three years.

2. Scientific Software Integration (SSI): SSI awards target larger groups of PIs organized around common research problems as well as common software infrastructure, and will result in a sustainable community software framework. The effort targeted by a SSI award is up to a level roughly comparable to: summer support for three to four investigators with complementary expertise; three to four graduate students; one or two senior personnel (including post-doctoral researchers, software developers, and staff); and their collective research needs (e.g., materials, supplies, travel) for three to five years. The integrative contributions of the SSI team should clearly be greater than the sum of the contributions of each individual member of the team.

3. Scientific Software Innovation Institutes (S2I2): S2I2 awards will focus on the establishment of long-term community-wide hubs of software excellence. These hubs will provide expertise, processes, resources and implementation mechanism to transform computational science and engineering innovations and community software into robust and sustained tools for enabling science and engineering. S2I2 proposals will bring together multidisciplinary teams of domains scientists and engineers, computer scientists and software engineers, technologists and educators.

The FY 2010 SI2 competition will be limited to SSE and SSI awards. The solicitation in FY 2011, and in subsequent years, will outline funding opportunities for all three classes of awards (SSE, SSI and S2I2), subject to availability of funds.